This invention relates to the application of electrodes to ceramic piezoelectric transducers.
Piezoelectric transducers must be provided with electrodes which have good electrical coupling to the piezoelectric transducer surface in order to produce the maximum possible deformation of the transducer in response to applied electric potentials. Ceramic piezoelectric transducers of the type used in ink jet systems, such as shear mode transducers which are in the form of a thin plate or layer of ceramic material like lead zirconium titanate (PZT), must be provided with a series of closely spaced electrodes on one or both surfaces. Heretofore, because of the granular surface structure of such ceramic materials, it has been necessary to apply electrodes to those surfaces by evaporating or sputtering thin layers of metal, such as copper or gold, onto the surfaces in order to provide high capacitive coupling, before subjecting the piezoelectric layer to an electric field to pole the piezoelectric material.
Conventional poling techniques for such piezoelectric transducers require that the electrode metal be applied in that manner to both surfaces before the piezoelectric material is polarized in order to obtain maximum polarization. Thereafter the previously applied electrode metal may be patterned by photolithographic etching techniques to provide electrodes at the desired locations on the opposite surfaces of the piezoelectric layer.
Recently, however, poling techniques for polarizing piezoelectric transducers have been developed which do not require prior application of metal layers to the transducer surfaces. For example, in the copending Moynihan et al. application Ser. No. 08/460,393 filed Jun. 2, 1995 now U.S. Pat. No. 5,605,659 and its parent application Ser. No. 08/406,297 filed Mar. 17, 1995, the disclosures of which are incorporated herein by reference, pressure poling and corona poling techniques are disclosed which eliminate the need for the presence of electrodes on the surfaces of the transducer material for poling of the material.
Furthermore, since the application of electrode material to the surfaces of piezoelectric materials by conventional evaporation or sputtering techniques is a complex procedure and represents a substantial portion of the cost of producing electroded piezoelectric transducers, it would be advantageous to provide a way of electroding piezoelectric transducers without requiring such complex and expensive steps. In addition, conventional piezoelectric transducers have electrodes which cannot be extended beyond the area of a surface of the transducer and thus require connection to remote actuating circuits by separate electrical leads, adding to the complexity and expense of manufacture.